The present invention relates to fluorescent lamp adapters, and in particular, to a device for powering a pair of fluorescent lamps independently and selectively.
Fluorescent lamps are known for their energy efficiency. Fluorescent lamps are often chosen over incandescent lamps to reduce power consumption and heat generation. With this in mind, a large market exists for retrofiting various types of lamp fixtures originally designed to accommodate incandescent lamps.
A difficulty with retrofiting existing incandescent lamp fixtures is the room needed for the complete circuit. A fluorescent lamp circuit usually requires a relatively large ballast and, perhaps, a starter. These bulky components can hamper mounting a fluorescent lamp in an incandescent light fixture. For example, the harp typically fitting around the socket of an incandescent table lamp restricts the space available for fluorescent lamp adapter.
In U.S. Pat. No. 4,683,402, a fluorescent lamp adapter uses a toroidal ballast that fits around a fluorescent lamp socket. This design reduces the overall volume of the adapter and allows screwing of the adapter into a conventional incandescent lamp socket.
In U.S. Pat. No. 4,645,283, a fluorescent lamp adapter has its ballast detachably connected to the side of the adapter case. This side-mounted ballast can be removed to provide clearance so the main case can be screwed into a lamp socket. The threaded base of the adapter base will ratchet to allow turning even after threading is complete. Once the main adapter case is properly positioned, the side ballast can be attached. See also U.S. Pat. Nos. 3,953,761; 4,363,083; and 4,841,193.
The well known three way bulb has dual filaments within a single glass envelope. This bulb typically has a screw base with three contacts for allowing individual and simultaneous powering of the two filaments. The above patents do not consider retrofiting the lamp fixtures designed to receive a conventional three way light bulb. These references do not disclose either multiple fluorescent lamps or adjusting the drive to the lamps.
A retrofit adapter for simulating a three way light bulb faces special difficulties. The ballasts for enabling a three way fluorescent lamp tend to run hot. Also when multiple ballasts are used, they occupy a significant amount of space. As noted above, a bulky adapter can be difficult to mount in an incandescent lamp socket. Furthermore, the ballasts must be positioned to allow efficient heat dissipation, so that the adapter does not become excessively hot.
Accordingly, there is a need for a compact adapter that can simulate a three way incandescent light bulb. The adapter ought to be designed to operate at a safe temperature.